Royal family Christmas cards have been released to the public regularly for decades. Some, namely those featuring the late Princess Diana with her then-husband Charles and sons William and Prince Harry, have also been sold at auctions.

See Royal family Christmas cards through the years:

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1942

A Christmas card from Princess Elizabeth, who would become Queen Elizabeth II of Great Britain, to the Grenadier Guards regiment of the British Army during World War II.

1999

2012

Prince Charles and Camilla, Duchess of Cornwall, take part in The Thames River Pageant, as part of the Diamond Jubilee, marking the 60th anniversary of the accession of Queen Elizabeth II.

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2013

Prince Charles and Camilla, Duchess of Cornwall, watch horses in the parade ring from the Royal Box on the second day of Royal Ascot.

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2014

Prince Charles and Camilla, Duchess of Cornwall, appear at the Invictus Games Opening Ceremony.

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2015

Prince Harry is seen with Battle of Britain veteran Tom Neil during the commemoration of the 75th anniversary of victory in the Battle of Britain at Goodwood Aerodrome in West Sussex. The Prince said the meeting was one most memorable moments of 2015.

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2015

Prince William, Kate Middleton, Prince George and Princess Charlotte appear in a photograph taken the previous October at Kensington Palace.

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2016

Prince Charles and Camilla, Duchess of Cornwall, appear on a royal tour of Croatia, where they met local performers wearing traditional dress in Tvrda, the old town of the city of Osijek.

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2017

Prince William, Kate Middleton, Prince George and Princess Charlotte appear in a photograph taken earlier in the year, before the Duchess of Cambridge's pregnancy with her third child was revealed.

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2017

Prince Charles and Camilla, Duchess of Cornwall, are pictured in July in the Orchard Room at Highgrove House on her 70th birthday.

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In 1942, during World War II, Queen Elizabeth II, then Princess Elizabeth, sent a Christmas card bearing her portrait to the Grenadier Guards regiment of the British Army.

"It is a great honor and privilege to have been appointed colonel of the Grenadier Guards and I shall do all in my power to uphold and foster the great traditions of the regiments which I have already learned to love," the card reads, along with a handwritten message that says, "Wishing you a very merry Christmas and Happy New Year."